premium serves different purposes.
the " good " is mostly subjective and really depends from someone needs.
generally, they help you to progress campaign points " faster " and quicker.
some of them comes with unique camouflages & weapons, others with fully upgraded tanks and what not.
you either buy them because you like them as they are, or buy some others as a " tier " skip.
( such as the panther A in berlin premium, or jumbo in normandy … for example. ).
then you have overall good premium tanks such as dicker max, jagdpanther, some of the premium airplanes with big bombs, and yada yada yada.
although, you might find " questionable " premium squad such as the moroccan one, or the volkssturm.
usually, picked more for the appearance / details of history behind them.
they are not meant to be better overall than free counterpart.
some of them are, others not so much.
but offers variety.
so, the question is, what do you need, and what do you want.
( above all. your wallet. i’d usually suggest to wait for discounts. because for those price, not really much is worthed outside the BA-11 and very, very few others cheap squads with good items )